Process of and apparatus for bleaching flour



Ju'ne 6, 1939. c. H. SMITH Y PROCESS OF AND APPA'RATUS FCR BLEACHING FLOUR Original Filed April 1, 1929 4 Sheets-Sheet l 0 7 m WQ T 7 /1 C es June 6, 1939. c. H. SMITH A l 2,160,918

PROCESS OFAND APPARATUS FOR BLEACHING FLOUR Original Filed April 1, 1929 4 Shets-Sheet 2 C. H.' SMITH June 6, 1939.

lPROCESS OF AND APPARATUS FOR BLEACHING FLOUR Original Filed April l, 1929 4 Sheets-Sheet 3 June 6 1939 c. H. SMITH 2,160,918

l PROCESS OF AND APPARATUS FOB BLEACHING FLOUR original Filed April 1, 1929 4 sheds-sheet 4 L73 lI lHilIIlllIIIIIIllllllllllllllllllllil "lumi In y In.,

l mmllll r formity of bleaching ac'tion throughout the mass bleaching chamber is usually in the form of a. 5

A further object of the invention is the propropelled through the machine from the point of 1.0

. 2,-, While the said process is not limited inits broad flour as it passes through the machine. Thus the :zo From the beginning of the art of bleaching ered at the mill andis not known until complaint i 45 1 Attempt has been made heretofore to accomsary to use an excess of the latter. which is'unde- `445 ...ama June 6.1.1939l y i y v 2,160,918

lwirr-:D'STATES PATE-Nr oFFIcE Pnocrzss oFAND APPARATUS Fon.. BLEAcmNG FLoUa campbell neuk smith.' Knoxville, Tenn., signor to J. Allen Smith & Company, Knoxville, Tenn., a' corporation of Maine f Application Apri; 1,1929, serial No. 351,51'z

August 3,1938

as; claims. (ci. ca -42) This invention relates to improved meansbrought into commercial use so constructed that process and apparatusfor the bleaching'of iiour, the tlour is stirred up into a cloud and sub- Its general object is to accomplish that opera` jected, while in that condition to the action of a tion in a thoroughly eillcient manner, with unibleaching gas. In apparatus of this class the of our, and without injury to, or detrimental horizontally disposed cylinder or drum, within effect upon, the product, either through the overwhich are a series .of revolving beaters, paddles, bleaching of any part thereof, or from other or equivalent devices, whereby the hour; is causes. f whipped into a cloud, and whereby 4it is also duction of a maximum output of properly inlet at one end to the discharge orilice at the bleached our with a minimum quantity of other.

bleaching agentand with a minimum use of ma- One serious drawback attending the use of ,chinery, floor-space and power. machines of this type is that they are not self- 15 A further object of the invention ls the avoidcleaning; for the beaters do not come into contact 15 ance of certain objections and dliilculties,` herewith the inner surface of the drum, the result inafter described, (some of which are of a serious being that some of the ilor adheres thereto, character) that attend the use of the processes forming a crust; and this adherent crust is quickand apparatus now commonly employed for the ly overbleached, eventually becoming rancid and 20 bleaching of flour. acquiring an exceedingly obnoxious odor. It is, of zo The invention comprises a, novelprocess and course, inevitable that from time to time some novel apparatus, by means of which the above of this overbleached and rancid' crust will be and other desirable objects are successfully acjarred looseand will be disintegrated by the a'ccomplished. tion of the beaters and commingled with the fresh aspect to the use of any particular bleaching gas latter is more or less contaminated; and inasmuch or agent, it is specially adapted for use with as the full effect of the overbleaching does not nitrogen trichloride, the trade name whereof is develop for some little time, it often happens that Agene. the contamination of the product is not Idiscovfiour by the action of a gaseous bleaching agent, is received from a customer. Heavy losses often effort has been made to devise means-process result: instances being kIlOWD in which 0115110111- and apparatus-such as would insure the uniform ers, finding one barrel of a shipment thus conexposure of all particles of the flour to the eifectaminated, have -shippedhqt'vholel car loads back tive action of the said gaseous agent. It has to the producing mills. Thisis one of the reasons been recognized that uniformity of bleaching efthat make uniformity of exposure of all parts of iect throughout the entiremass of the flour is of the mass of flour to the action of the bleaching the highest importance, but it has not been found gas, and the self-cleaning feature, with the avoidpossible, with the means heretofore available, to ance of overbleaching, so highly desirable. .L attain that result commercially. On thel other Furthermore, it hasalsobeen -found. that the 40 hand, it is highly important also, for reasons flour passes through a machine of the horizontal stated below, that no excess of gas be used, that cylinder type described above too quickly for the no part of the iiour be over-bleached, and that proper absorption of just the right amount of the 'apparatus be thoroughly self-cleaning. certain kinds of bleaching gases, making it necesplish the. bleaching of flour commercially` with sirable for various reasons.

the aid of gaseous agents by subjecting the mass With the object of avoiding the objections and oi' our while passing through the bleaching diiculties experienced with the above described chamber to agitationof such sort as to convert horizontalI cylinder type of bleachers, and of no it into a cloud of dust; the theory being that in bringing about Vthe theoretically correct degree that form the bleaching gas can diffuse itself with and duration of contact between the bleaching @proximate uniformity i throughout the entire gas and 'the individual particles of the mass of mass and thus act effectively uponl every particle flour, vertical machines have been devised. These of the ilour. are sometimes circulmnd sometimes angular in 55, Machines of various types have ben devised and cross section. 'Ihe formergre equipped with a 55 plurality of revolving disks which spread the our into a thin sheet as it passes through the machine; Whereas the latter are furnished with horizontally rotating beaters that whip the our into a cloud. But even in machines of the vertical type the adherence of particles of flour to the walls of the chamber with consequent overbleaching of the encrusted particles and contamination of the entire product, is not wholly avoided. Moreover, the our passes through this vertical type of machine as through those of the horizontal'cylinder type, with such rapidity that it does not have the time required for the proper degree and duration of contactwith certain kinds. of bleaching gases or agents, the result being that a considerable excess of the latter is used in order to bleach the our to the desired degree of whiteness.

It should be observed that the rapid passage o'f thefiour through the bleaching chamber is not objectionable when chlorine is used as the bleaching agent, since the action of that gas is almost instantaneous. The objection to the rapid transit of the flour through the machine developswhen one of the more slowly acting gases (such as nitrogen trichloride)r is used; vthe latter,having come into wide use in the past few years.

It should be further observed that it is not entirely for economys sake that the use of an excess of the'bleaching gas should be avoided; for

the cost of the bleaching gasesor agents is relatively small. The importance of avoiding overexposure of any part of the flour to the action of the gas is because of the effect thereof upon the flour itself. The latter is permeated with a vegetable oil in which resides a yellowish coloring matter (called Carotin because of its resemblance to the color of the vegetable carrot) and the object and effect of the bleaching operation is to decolorize the cartin by oxidation. changing it from yellow to white. The important point then is that the action of the bleaching agent-should go far enough to decolorize the carotin sufficiently but should not be allowedto goY farther than necessary for the accomplishment of that object, because, if carried farther, the gas oxidizes the vegetable oil itself, producing rancidity. And, as already stated, it frequently happens that the effect of an 'excess of contact between the gas and the ilour,(or parts of the mass of the latter) does not develop to the point of a manifestation of rancidity until the lapse of a week or more. It will thus be clearly seen that, in all cases where the transit of the flour through the bleaching chamber is too rapid, it is necessary t0 use an excess of the bleaching gas, with the attendant danger of producing the deleterious eects described above.

According to the present invention, the flour is not converted into a cloud and exposed to the action of the bleaching gas while suspended in the air, but on the contrary is spread out into a very thin or shallow stream, and in that form is conducted slowly through the bleaching chamber. This essential part of the process may be accomplished in a variety of ways, some of which will be specifically described hereinafter.

The bleaching gas is admitted ,in regulated quantity at a suitable point or points so that it diffuses itself throughout the bleaching chamber; the result being that the flo durin'g its transit through the apparatus, is lilconstant contact with the gas. Indeterminin necessary for theabsorption of the proper amount of gasl by the our, the principal factors are the` the length of time height 'of the apparatus, the number of trays therein, and the speed at which the trays are gyrated.

While ordinarily the bleaching agent is in the form of a. gas generated outside the bleaching chamber and admitted thereinto by a suitable inlet or inlets, the invention may be carried out by the use of powders which,'when mixed with the flour, liberate ableaching gas. Several powdersof that character are available.

But for the full accomplishment of the objects of this invention something more is required besides causing the flour to pass through thebleaching chamber in a .wide and shallow stream; namely, that the particles of the stream of our While in transit should be constantly changing their relative positions, so that all the particles wil be equally acted upon by the bleaching agent; in other words, so that thev bleaching action may be uniform throughout the mass of product.

The most effective method thus far found of producing the two-fold motion referred to above-viz. (1) the slow travel of the flour through the bleaching chamber in the form of a widely spread, shallow stream, and (2) the constant shifting of the relative positions of the particles composing the stream-is by imparting to the trays, ledges, shelves or other elements over the surface of which the flour stream passes, a rapid and somewhat energetic gyratory motion.

Machines of various types capable of imparting the desired motion for other purposes (as for sifting) are already in general use, and can readily be reorganized, or,l reconstructed as hereim after described, so as to be adapted for use in carrying out thepresent invention.

`Successful results have been obtained-that is to say, a large production of flour thoroughly and uniformly bleached-by the use of an apparatus comprising stacks of trays horizontally disposed one above another, the arrangement beingy such that the stream of our pursues a zig-zag course, changing the direction of its travel when it drops from one tray to the next. But the rays may/be more or less inclined, either vfixed in position or made adjustable to any desired angle. And instead of disposing the trays one above the otherv and causing the stream of flour. to reverse the direction of its movement, the trays may be disposed after the manner of a spiral stairway, according to the arrangement of the sieves of the Allis-Chalmers sifter. Or the arrangement may be that of a straight stairway; or any of a num ber of other arrangements may be used. In fact,

the process may be successfully carried out in an apparatus constructedafter the general pattern of any of the well-known kinds of flour sifters now in use, each sieve being given an imperforate bottom to constitute a. tray and being so formed as to spillV the flour off one end`onto the tray next beneath, and the apparatus being so constructed and organized that the our traverses the surface of each of the series of gyratory elements successively.

tion illustrating another form of apparatus suit- 'able fork carrying out the new process;

Fig. 7 `is a horizontal section and plan on line 'I-l (Fig. 6);

Figs. 8, 9, and illustrate still another form of apparatus that may be usedr in practicing the process herein described, Fig. 8` being a side elevation, Fig. 9 a vertical section on line 9--9 (Fig. 8) and Fig. 10 a horizontal section on line Ill-I0 (Fig. 9); A

Fig. 11 is a vertical section, on a larger scale, of one of the trays shown in Figs. .8-10.

Figs. 12v-15 illustrate a bleaching' apparatus constructed on the plan of the Allis-Chalmers sifter, Fig. 12 being a top plan view, Fig, 13 a sideelevation, Fig.v 14 a partial perspective uiew (on an enlarged scale) showing the arrangement of the trays relative Ato each other, and Fig. 15 a diagrammatic'view showing the paths of the several flour streams.

The vbleaching apparatus illustrated in Figs. 14, which is shown by way of example only, comprises a series of boxes or'trays I5, of idenandhaving a'ila-t imperforate bottom or floor '|6, the box or tray being made of wood, hard rubber, sheet metal, or other material, preferably one not affected by the corrosive action of the bleaching agent.

At one end of each tray and extending from side to side thereof is an aperture or preferably a series of narrow apertures orslits I l, which may be formed by parallel wires set close together, between which the flour, after having traversed the floor I6 of the tray, drops to the one next beneath. 'I'he wires assist in splitting up the stream of flour as it falls between them, thusfacilitating the contact of the gas with all particles of the mass of flour. Y

In stacking the trays one above another they should, of course, be alternately reversed 'as shown in Fig 3, so that the discharge end of each tray is directly above the imperforate end of the supported, and the means whereby the required vibratory motion is imparted thereto,may be of various. sorts. The structure and actuating mechanism illustrated in Figs. 1-3 are in all essential respects the same las those of a wellknown our sifting apparatus. The apparatus as shown comprises four sets A, B, C, D, of trays stacked vertically (though the number of traws may be more or less), 'each set being provided with an inlet I8 for the flour at the top and an outlet I9 therefor at the bottonr` Except for said openings each set of trays is made nearly air-tight, this being accomplished in any suitable way, as` by interposition of a packing strip,

of felt, rubber or other suitable material, be-

tween the'tQp vedge of each tray (to which edge said packing is preferably secured) and the bottom of the tray. above. Y

'Ihe entire structure is suspended from a suitable overhead support by flexible hangers 2'0, which usually are rods of wood'Y or metal; the object being to permit a certain extent of gyration in an approximately horizontal plane. This vibratory motion is commonly produced, in the type of apparatus shown in`Figs. 1-3, by means of a crank shaft 22, 2'3, journaled in a step 2l,

and journaled also in the top and bottom cross pieces 25, 26 of the frame. The shaft carries a counterbalance weight 2l and is driven by a.

belt 28 and pulley 29.

The gasi inlets 3|),` which pass through the Sides of the casing IIa, are preferably located nearer the top than the bottom of the apparatus,

and far enough from the top to insure that no gas will escape at the our inlet. It is easy to ascertain by experience how far below the top the gas inlets should be located.

In order to insure the successful bleaching of the flour, and specifically to prevent the arrest and consequent overbleaching of particles of flour aggregated in small masses, means are provided which may be, designated generically as self-cleaning" means. These may be of various sorts, preference being given to such as cause a jarring or concussion of the trays and of any surfaces with which the flour makes contact in its transit through thev apparatus. As shown in Figs. 3 and 4 the self-cleaning action is effected by means of solid objects 3|, one or several in each tray, and loose therein.

These loose solid objectsare shown in Figs. 3 and 4 as spherical in form, but they may be of any suitable shape. They may be made of wood, hard rubber, or other suitable material. Their main function is to strike against the sides of the tray in which they are located and the bottom of the tray next above and by concussion to jar olf any particles of flour that may tend to adhere to the walls thereof. They serve also to assist somewhat in stir-'ring up the flour and thus bringing all particles thereof into contact` with the bleaching gas.

It isldeemed desirablel as a precaution against the lodgrnent of flour in the corners of the trays to fill the corners with angle pieces 32.

The operation of' the apparatus is obvious. The mass of flour entering at I8 is caused. by the gyratory motion of the apparatus to spread out over the floor I6. of the uppermost tray and to traverse the same slowly; and inasmuch as all the flour that reaches the apertured part of the tray drops to the next tray beneath, the flow of the stream of flour is-thereby determined toward that end. When the trays are grouped and stacked as in Figs. 1-3 the direction of the stream is alternately reversed; but according to other arrangements of the trays, ysuch as described below, thel direction of the flour stream is not l reversed. In the course of the slow ytraverse of the stream of flour from one end to the other of each tray there is, of course, a continual turning over and over of the individual particles, and a shifting of the relative positions of said particles, such as to bring them all into effective contact with the bleaching gas; the result being, as has been fully demonstrated in practice on a commercial scale, that the flour issuing frorr the discharge orifices I9 is bleached uniformly, .and bleached thoroughly without overbleaching of any part. over, with a minimum quantity of bleaching gas vand without th`e danger of any particles of flour being arrested in their progress through the machine and retained therein longer than the requisite time for proper bleaching.

In the apparatus shown in Figs. 1-4 thel trays I5 are arranged so that the plane imperforate surfaces over which the flour travels are horizontal. But in some cases it is, or may be, deemed desirable to quicken the travel of the flour stream; yand for that purpose, or for other reasons, the trays may be arranged with their oors slightly inclined though still approximately horizontal. In such casethe solid objects 3| of Figs. 3 and 4 if -loose might not act effectively,

since they would tend to gravitate to the depressed ends of the-trays. Therefore', as shown in Fig. 5 the self-cleaning means may consist of the chains 33, which extend from end to end of the tray and which are attached thereto at each end, as by means of the screw eyes or staples 34. The chains are long enough to be quite slack, and to them are attached at intervals pieces of rubber or other material 49, which may be spherical as in Fig. 5, or cubical as in Fig. '7. The vibratory motion of the apparatus causes these freely dangling chains to sweep over the floor of the tray and to strike forcibly the sides thereof, thus eiectuallypreventing the adherence of particles of flour to any part of the tray.

In Figs. 6 and '7 is illustrated diagrammatically another form of apparatus that is suitable for carrying out the process. The scheme of this apparatus somewhat resembles a type of flour sifter in commercial use, known as the Rotex.

In this apparatus there is no casing that encloses all of the trays, each individual tray I5 being made airtight. although as shown in Fig. 6 the inclination is somewhat exaggerated, and each communicates with the one next beneath it by means of an impervious flexible tube or. stocking 35. At its high or receiving end, each tray is supported and given a rotary vibratory movement by a crank pin 36 loosely engaging an opening in a bracket arm 37 secured to the tray. At each side of the low or exit end of each tray there is a slide block 38 secured to the tray by-a pivot pin 39. Each slide block works freely in a slideway or groove'in.

a support 40, whereby each tray is supported at its low end to move backward and forward -with a slight sideways movement. Each stocking 35 ls to be made suiciently long and full to accommodate the difference of movement .of the trays at the point where they are in communication through the stocking. As shown in Fig. '7, each tray is provided with chains 33 and solid objects 49 (square blocks in this instance).

Figs. 8, 9 and 10 illustrate diagrammatically an apparatus patterned after the plan of what is known as the "Plansifter type of flour sifters.

This apparatus comprises four or more sectionsor stacks of trays, A, B, C, D, ,(Flg. 8) which are arranged side by side and ar supported by the ilexible hangers 20. The lprincipal difference between this apparatus and that shown in Figs. 1-4 is that the more elongated trays are equipped with carrier nights 43 which are placed along the side of the trays and'act as a means of propelling the flour toward the discharge end of each tray. As shown in Fig. 1l, a strip of wood 45 is placed across each tray at a distance from the bottom sucient to allow the our to pass underneath it, the purpose of the stripes being to keep the solid objects 49 properly distributed in the trays and not to allow them to collect at the discharge end of each tray where they would otherwise be propelled by the carrier flights.

Figs. 12-15 illustrate a reorganized sifter ofl thel Allis-Chalmers type. The trays I5 are of trapezoidal forni,l and are identical in size and shape. In the example illustrated they are arranged in three groups, though the number of the groups is v-ariable. Each group is arranged after the manner of afspiral stairWay', the shorter side-5I of; each tray being towards the center of the apparatus. The threexspiralshave 'a common center, a'ndall are enclosed in an air-tight cylindrical casing 52, which is supported by exible suspension rods 20, and gyrated by power 'The several trays are inclined,

driven mechanism similar to that shown in Fig. 1.

The relative arrangement of the trays forming one of the spirals is illustrated in perspective in Fig. 14. The apertures I7 in each tray, through which the flour passes to the next tray beneath,

are in one of the vertical sides -(that adjacent to flour owing through the machine, each in a spiral path of its own, and each making ve drops to a 'lower level in the course of each turn of the spiral. These three separate paths are indicated diagrammatically in Fig. 15 which represents cylinder 52 as flattened out into a plane; one path being represented by a solid line 54, another by dotted line 55, and the third by a dot and dash line-56.

The three inlets I8 for the respective sefies. of trays are equidistant from each other degrees apart) and of course each inlet communi-- cates directly with the top tray of one of the series. The top tray of each series is directly above the third tray of the next series to the left (clock-wise direction) and its third tray down is directly beneath the top tray of the adjacent series to the right (counter-clockwise direction). It is, ofcourse, immaterial which direction the spirals take. shown as in the form of disks.

Obviously, by appropriate alteration of sizes and proportions the cylinder could be made to accommodatetwo series of trays in spiral arrangement, or four, or even a larger number.

It isqobvious that in certain of the forms4 of apparatus shown one set (or several) of the trays could have foraminous bottoms, so as to `act as sieves, and thus the two operations of sifting and bleaching could be carried on simultaneously. For example, referring to Fig. 2, the section D could be composed of sieves of the usual construction, while sections A, B and C could have trays such as described herein. 'I'hus three' The loose solid objects 3| arel deemed to be an important practical advantage of the present invention.

In the case of a mill whose capacity is so small asnot 'to require a complete 4sifter to be used `for bleaching, a small bleaching apparatus may be mounted as an independent unit on top of thesifter and thus receive its required vibratory motion indirectly through the latter.,

Another advantage realized by the present invention is the great saving in power and in Cthe amount of machinery required relatively to a given output. Thus it-has been found by experience that an'- output which formerly required sixteen agitators of the horizontal cylinder type,

'driven by belts aggregating eighty-two inches in width, may be (and now is) obtained by using three sections of one sifter driven by a four-inch belt. There is a corresponding saving in the number of controls" which are supplied by the manufacturers of the bleaching apparatus for metering the gas supplied to the bleaching apparatus; and there is also a corresponding saving in oor space in the mill. i What is claimed is: Y

1. A process of bleaching flour which includes delivering the flour4 onto an approximately hori-- zontal plane imperforate surface; Kimparting to said surface approximately horizontal gyratory movement such as to cause the flour to be spread upon and to travel over and oif said surface with simultaneous shifting of the flour particles relative to each other during said travel; confining the flour to said surface during its travel thereover;aand bringing a bleaching agent into vcontact with the flour While it is traversing said surface. o

2. A process of bleaching our which includes delivering the flour onto the uppermost of a plurality of approximately horizontal plane imperforate surfaces arranged at descending levels; imparting to said surfaces approximately horizontal gyratory movement such as to cause the flour to be spread upon and to travel over and off each surface with simultaneous shifting of the iiour particles relative to each other and to fall from each upper surface onto a lower surface; and bringing a bleaching agent into contact with the flour while it is traversing said surfaces.

3. A process of bleaching flour which includes delivering the flour onto an approximately horizontal plane imperforate surface imparting .to

said surface approximately horizontal gyratory movement such as to cause the our to be spread upon and to travel over and off said surface with simultaneous shifting of the our particles relative to each other during said travel; confining the flour to said surface during its travel thereover bringing a bleaching agent into contact with the flour while it is traversing said surface; and repeatedly jarring said plane imperforate surface.

4. A process of bleaching flour which includes delivering the our onto the uppermost of a pluralityl of approximately horizontal plane imperforate surfaces arranged at descending levels imparting to said surfaces approximately horizontal` gyratory movement such as 4to cause the iiour to be spread upon and to travel over and oil.' each surface'with simultaneous shifting of the flour particles relative to each other and to fall from each upper surface onto a lower surface; confining the flour toA said surfaces during its travel thereover; and bringing a bleaching agent-into contact with the flour while it is traversing said surfaces. i

5. The process as specified in claim 4. with the further step of repeatedly jarring said plane imperforate surfaces. o

6. A` process of bleaching our which includes delivering the flour onto the uppermost of a plurality of approximately horizontal plane imperforate surfaces arranged at descending levels in an enclosure; imparting to said surfaces approximately horizontal gyratory movement such as to* cause the flour to be spread upon and to travel over and off each ysurface with simultaneous shifting of our particlesrelative to each other and to fall from each upper surface onto a v-lower' surface; conningthe flour 'to said surfaces during its .travel thereover; introducing a bleaching gyratory movement to said trays.

repeatedly jarring said plane imperforate surfaces.

'7. A process of bleaching flour which includes delivering the our onto the uppermost of a plurality of approximately horizontal plane imperforate surfaces arranged at descending levels in an enclosure; imparting to said surfaces approxi- 9. The process specified in claim 7, with the I further step of repeatedly jarring the surfaces over which the our travels.

10. Apparatus for treating flour with a bleachin g agent said apparatus having openings for the inlet of fiour and bleaching agent and for the outlet of fiour and including in combination a tray through which the flour passes in travelling from said our inlet to said flour outlet, said tray having an imperforate plane inner bottom surface approximately surrounded by an upright rim or flange constituting a part of the tray; means for supporting the tray with its said bottom surface approximately horizontal; means for imparting approximately horizontal gyratory movement to said tray and means for conning the bleaching agent to the zone of treatment, said zone comprising the path .traversed by the our in passing through the tray.

l1. Thev combination as specified in claim l0, with the addition of means freely movable in the tray for imparting thereto repeated jars or concussions. i 12. An apparatusy for treating flour with bleaching agent having in combination openings .for the inlet of our and bleaching agent andfor the outlet of flour; a plurality 'of trays through which the our passes in travelling from said fiour inlet to said flour outlet, each tray having an imperforate plane inner bottom surface;

means for supporting said trays at different levels each with its said bottom surface approximately horizontal and with the trays in Suchrelation that each upper, tray delivers flour through an exit opening thereof to a lower tray; and means for imparting approximately horizontal gyratory movement to said trays.

13. The combination as specified in claim 12, with the addition of means freely movable in the trays for imparting thereto repeated jars or concussions. e

14. An apparatus for bleaching flour having in combination openings for the inlet of flour and bleaching agent and for the outlet of flour; a plurality of trays through which the flour passes in succession in travelling from said fiour inlet to said flour outlet, each tray having an imperforate plane inner bottom surface; means for supporting said trays at different levels with the bottom surface of each approximately Chorizontal and with the trays in such relation that each upper tray delivers flour through' an exit opening thereof to the next lower tray; and means for imparting approximately horizontal 15. The combination specified in claim 14, with the addition of means freely movable in the trays for imparting thereto repeatedv jars or .concussiona 16. An apparatus for bleaching fiour having in combination an enclosing casing supported for gyratory movement and having openings for the inlet of our and bleaching agent and for the outlet of flour; a plurality of trays positioned one above another in said casing through which trays the vflour passes in succession in travelling from said iiour inlet to said flour outlet, each tray having an imperforate plane inner bottom surface over which the flour travels and each upper tray delivering flour through an exit opening thereof to the next lower tray; means freely movable in one or more of said trays for imparting thereto repeated jars or concussions; and means for imparting approximately horizontal gyratory movement to said casing and the trays therein.

17. An apparatus for treating our with bleaching agent said apparatus having openings for the inlet of flour and bleaching agent and for the outlet of flour and including in combination, a plurality of trays through which the flour passes in travelling from said flour inlet to saidl fiour outlet', each tray having an imperforate plane inner bottom surface approximately surrounded by an upright rim or flange fixed to said surface; means for supporting said trays at different levels each with its said bottom surface approximately horizontal and with the trays in such relation that each upper tray delivers our through an exit opening thereof to a lower tray; means for imparting approximatelyv horizontal gyratory movement to said trays and means for confining the bleaching agent to the zones of treatment, said zones comprising the path traversed by the flour in passing through the trays.

18. The combination specified in claim 17, with .the addition of means lfor repeatedly jarring said trays.

19. vApparatus for treating our with a bleaching agent having in combination a casing having openings for the inlet of our and bleaching agent and for the outlet of flour; a tray through which the flour passes in travelling from said our'inlet to said flour outlet, said trayN having an imperforate plane inner bottom surface approximately surrounded by an upright rim or flange and also having a discharge opening through which flour passes from said inner bottom surface; means for -supporting the tray with its said bottom surface approximately horizontal; and means for imparting approximately horizontal gyratory movement to said tray.

20. The combination specified in claim 19, with the addition of means for repeatedly jarring the surface over which the flour travels.

21. An apparatus for treating flour comprising an enclosure, a series of removable imperforate traysat different levels therein, each tray communicating by suitable outlet with the next one beneath it in the series, said trays being arranged in the form of a spiral stairway, said apparatus having exible supporting means and power means for imparting vibratory motion thereto.

22. An apparatus for treating fiour comprising an enclosure, a series of removable imperforate trays of trapezoidal form at different levels therein, each tray communicating by suitable outlet with the next one beneath it in the series, said trays being arranged in the form of a spiral stairway, said apparatus having flexible supporting means and power means for imparting vibratory motion thereto.

23.` An apparatus for treating flourcomprising an enclosure,a plurality of series of imperforate trays at different levels, each series of trays having an independent flour inlet and ilour outlet so as to constitute a continuous passageway for a stream of flour through said apparatus, each individual tray communicating by suitable outnlet with the next adjacent one in the same series, 

